What is your Air Fuel Ratio? Scan-Guage II

[phattyduck]

I freaking love you!!! thank you!

I was close, got the TXD and RXD the same, the RXF was off 1 number... and well the MTH was off...

plugged it in after my drive to work, just sitting in the parking lot, it was up-dating very quick... I was reading 14.5-15.3 at idle... can't wait to see it going home...

now it is kinda odd... I haven't driven with it yet, but the numbers didn't seem so stiff as you're describing...

The single number different in the RXF field tell the scangauge where to put the decimal in the display. The math is where you get 14.7 reference and the right order of magnitude. I mixed the codes for the AFR sensors and the O2 sensors, basically...

It is just odd that Toyota put that data under the "O2" sensor reading instead of an AFR sensor reading.

-Charlie

 

[SnowLizard]

Driving round town I'm consistently 14.9-15.4 it does go lower but I fear I'm just lean...

So I think I have an exhaust leak...
It would cause a leaness
Makes the engine fluctuate to get the perfect reading wasting fuel dumping more fuel but then leaks so it doesn't know its true afr

 

[phattyduck]

Driving round town I'm consistently 14.9-15.4 it does go lower but I fear I'm just lean...

So I think I have an exhaust leak...
It would cause a leaness
Makes the engine fluctuate to get the perfect reading wasting fuel dumping more fuel but then leaks so it doesn't know its true afr

You are reading way to much into this. Check your short term and long term fuel trims. If they are good (close to 0) and you are getting reasonable mileage, everything is fine.

-Charlie

 

[SnowLizard]

You are reading way to much into this. Check your short term and long term fuel trims. If they are good (close to 0) and you are getting reasonable mileage, everything is fine.

-Charlie

it's possible... but here is what I know as facts...

I have a 97 4runner, stock, even tires...
My 99 was is my daily driver, before the lift and tires... I got 15mpg vs the 97 getting 18...

1- both are the same, except the gear ratio (4.10 vs 4.30)
2- the 97 accelerated and still does, faster than the 99
3- I understand bigger tires will hurt mpg. I am running 285/70 r16 (odd size from nitto trail grappler's M/T) and I'm now down to 14-15mpg... ok I'm at 14mpg.
4- my wifes 97 has stay consistant, 18mpg, mixed driving, and trust me when I say she's 'always' in the throttle... and brakes later. she shouldn't be getting that mpg, and when I drive it... I've reached 19mpg with the way I drive, and I drive both 97 and 99 the same.
5- both are auto's
6- both are 4wd's
7- mine does have e-locker... her's does not
8- 97 is Sr5 and 99 is limited, awd is off.
9- 97 exhaust smells 'good', for an exhaust smell... 99 smells bad, not 'rotten egg' or anything but 'thick' and 'over powering'... it just smells off... I have confirmed from two other 3rd gen 4runners I have 'test' drove from craigslist. they smell like the 97, one was 99 and the other was a 02


my lift is only 2inches, I've have read these forums and everyone I've asked is average 16 for 33's and 3 inch lift. I'm 13.7-14.5mpg

I bet if I took my lift back off and ran stock tires, the 99 would not get better than 16... freeway 17 maybe.

ok, so that's my facts...

I do have a new O2 sensor... it could be bad, but no code...
I do have new CAT's... yes both cats, both are walker from rockauto
I have done PM... sensors/intake/fuel/grease/fluids/filters/gaskets...

I'm thinking next injectors, possibly replace the auto-zoo fuel regulator ($160) I installed as a test... the stock one was better.

I'm thinking fuel, maybe i need a computer re-flashed... I've experienced that before in a chevy.

I'm not sure where to look at... the AFR is pretty darn close... and besides, if I'm really running 14.9+ wouldn't i get better mpg? just 'slightly' above?

idk, i might be reaching but i feel something is wrong, not catastrophic wrong, but something I want to fix. it's annoying me, and I want it gone.

 

[phattyduck]

If you aren't correcting for tire size, that would account for nearly 1 mpg all by itself. 4.3 vs. 4.1 gears is nearly 5%, but it won't be that much of a hit to mileage (maybe a couple %). A mud terrain tire will be worse for mileage compared to a highway-type tire. A lift (even 2") will decrease mileage slightly. Anything on the roof rack all the time?

Since you have a scangauge, check your fuel trims (long term and short term). If you have one bad/weak cylinder in the '99, it could be throwing everything off.

Before throwing more parts at it, you'll want to do more diagnosis...

-Charlie